Bio Notes Essay examples

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I. Evolution - Descent with modification; the idea that living species are descendants of ancestral species that were different from present day ones; also the genetic changes in a population over generations. *Changes over time

1. Ideas before Darwin a. Ancient Greeks b. Fossil Record c. Heritability was known but not understood d. 1800 - Jean Baptiste Lamark - evolution by inheritance of acquired characteristics. 2. Darwinian Evolution a. Heritability - the principle that offspring show the same genotypes and phenotypes as their parents.

b. Variation - In natural populations there is variations in genotypes and phenotypes resulting from them.

c. Selection - In natural populations some genotypes and phenotypes survive and reproduce more successfully than other genotypes and phenotypes. 3. Evolution by Natural Selection: a. First developed by Darwin the the 1830s b. Independently developed by Alfred Wallace in 1858. c. On the Origin of Species published in 1859.

4. Natural Selection produces adaptations. a. Adaptation - An inherited characteristic that enhances the organism’s ability to survive and reproduce in a particular environment. b. Types of adaptations: - Morphological - Structural; Anatomical - Physiological - organ/organ system function - Behavioral - Only in animals; how they act to attract a mate - Biochemical - Enzymes and Metabolism

c. Agents of Natural Selection: - Predators - Prey - Competition - Disease/Parasites - Extremes of climate and weather (physical environment)
II. Evidence for Evolution

1. Microevolution - A change in a population’s gene pool over generations * The change in allele frequency in a population over time as a result of natural selection.

a. Favored alleles increase in frequency -Example: Evolution of pesticide resistance in insects.

- Variation - In large populations, a few will carry for insecticide resistance.

- Heritability - The genes are passed from parents to offspring

- Selection - Use of DDT changed the selective environment - Example 2: Evolution of antibiotic resistance in bacteria

2. Macroevolution - Long-term changes over thousands or millions of years that produce a new species, new lineages, or major change within a lineage.

a. Fossil record - different layers = different ages in past - Fossils show pattern of change consistent with geologic age

b. Homologous structures and vestigial organs. *Descent with modification - Wings of birds/mammal forelimbs - Vertebrate skeletons - Bones in whale flippers, snake pelvis

c. Biochemistry and Molecular Biology - unity of origin : same biomolecules and metabolism in all organisms - closely related organisms have extreme similarity in DNA sequences - As more different organisms are compared, more DNA differences are found.

III. Microevolution in Detail 1. Origins of genetic variation a. Crossing-over during Meiosis I b. Independent assortment of chromosomes during Meiosis.

c. Fertilization --> new offspring genotype combination. d. Mutation - A change in the nucleotide sequence of an organism's DNA; mutation also can occur in the DNA or RNA of a virus; the ultimate source of genetic diversity; - Change in DNA sequence of a gene - very rare event (one in a billion) - random event - occurs naturally - Mutation rate increases with exposure to certain chemicals (mutagens) or high energy electromagnetic radiation. (UV Light; X-Rays; Gamma rays; Cosmic rays) - Most mutations have harmful effects or no effects 2. Microevolution - A change in a population's gene pool over generations; change in allele
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